The present invention relates to a vane for rotary fluid pump, and more particularly, to a type thereof in which an alloy layer having high wear resistivity, high resistance to thermal seizure, and high corrosion resistance is provided at a sliding surface of the vane by overlaid or build up welding. The present invention also relates to a method for producing the vane.
A rotary fluid pump is used in an air conditioner. One conventional rotary fluid pump is shown in FIG. 1, in which a cylindrical housing 21 is formed with a vane groove 21A extending in radial direction thereof, and a roller 22 is eccentrically rotatably provided within the housing 21. A shaft 23 is integrally fixed to the roller 22 for its rotation, and a vane 1' is slidably disposed in the vane groove 21A. The vane 1' is normally biased toward the roller 22, so that a radially inner end face or a nose portion of the vane 1' is in sliding contact with an outer peripheral surface of the roller 22. Such structure is well known in the art.
The conventional vane 1' is formed of cast iron or steel such as SKH 51 defined by JIS, Japanese Industrial Standard, which is a high speed tool steel containing 0.8-0.9% of C, 3.8-4.5% of Cr, 4.5-5.5% of Mo, 5.5-6.7% of W, 1.6-2.2% of V, and balance Fe. Further, a vane formed of aluminum or carbon is also used for the purpose of reduction in weight. In the vanes, generally, high wear resistance is required particularly at the nose portion which is in sliding contact with the roller. Therefore, there has been proposed a composite vane in which high grade material is provided at the nose portion, and a low grade material is used at the remaining portion of the vane. Such composite vane is provided by spraying or sintering method for providing the nose portion, and is also advantageous in production cost.
However, in case of the cast iron vane or steel vane, sufficient wear resistance may not be obtainable so as to withstand high friction attendant to high speed rotation of the roller which high speed is required for increasing pump output. Further, the carbon vane has inherent deficiencies such as high production cost, difficulty in machining, and insufficient wear resistivity. Furthermore, regarding the composite vane, the sprayed or sintered layer may be peeled off from the vane body due to insufficient bonding strength, and, sufficient material yieldability is not obtainable.
Japanese Utility Model Application Kokai No. 60-23282 and Japanese Patent Application Kokai No. 61-197781 disclose a composite vane whose nose portion is provided by fusing alloy powders by means of a heat source providing high density energy. That is, the alloy powders are accumulatingly mounted on an end face of the vane, and thereafter, the high heat energy is applied to the end face so as to melt the alloy powder in an attempt to obtain the vane sliding portion having high hardness. However, according to this method, alloy powders on the end face of the vane may be scattered when the heat source is applied thereto. As a result, yieldability may be lowered, and uniform dimension of the resultant sliding portion may not be obtainable, and further, various production steps are required.